This study examined samples part of a larger project exploring environmental changes at Lake Hawdon, mid Canterbury, involving Queen’s University Belfast and the University of Canterbury. The author was responsible for the analysis of 85 fossil diatom samples from Lake Hawdon to create a high resolution study to assess their use as a biological proxy of past environmental changes through the Late Glacial Inter-Glacial Transition. Qualitative interpretations suggest three main phases of environmental change in Lake Hawdon during ~17,000 to 10,000 cal. BP. The first is a cool stage where taxa such as Cocconeis placentula and fragilarioid complex taxa Staurosirella pinnata and Pseudostaurosira brevistriata suggest a cool shallow lake with increasing macrophyte growth. The second phase suggests cold deepening water from at 13,928 +/- 142 to 12,686 +/- 166 cal. BP, dominated by Pseudostaurosira brevistriata, which coincides with the Antarctic Cold Reversal. The third phase represents a warm deep water phase after 12,686 +/- 166 cal. BP, dominated by planktonic taxon Cyclotella stelligera and epiphytic taxon Epithemia sorex, suggesting that Lake Hawdon does not exhibit the Younger Dryas event. Pollen and chironomid data from Lake Hawdon, generated by other project members, are included in the quantitative analyses to further inform palaeoenvironmental inferences generated from diatom data. Chironomid temperature reconstructions complement diatom interpretations for all three phases of change in the lake however diatom resolution allows changes to be detected earlier than other proxies suggest. Stabilisation of the landscape ~12, 686 +/- 166 cal. BP is suggested by tree pollen appearing near the end of the diatom cold phase, confirming with the diatoms and chironomid data that there was a warming out of the cold phase. Interpretations from Lake Hawdon add to other proxy studies in New Zealand that suggest an Antarctic Cold Reversal type event, but fail to highlight the Younger Dryas event. The generation of a transfer function was attempted with the diatom data based on Northern Hemisphere datasets, but a Principal Component Analysis plot highlighted major dissimilarities between the New Zealand fossil data and modern European data. This raised the issue of having morphologically similar but genetically separate taxa, potentially displaying convergent environmental adaptation, a crucial area for further research globally, and particularly in isolated areas like New Zealand.

No description available.

Los Andes ecuatorianos, ubicados en el noroeste de América del Sur son considerados un “hot-spot” con una alta diversidad mundial de plantas vasculares, debido a su compleja topografía (elevación de la cordillera), variaciones de las condiciones climáticas y los distintos tipos de vegetación. A pesar de su elevado nivel de biodiversidad, los Andes ecuatorianos presentan uno de los paisajes más amenazados y poco estudiados. Especialmente los ecosistemas de páramo y montaña están sujetos a sobrepastoreo, quemas, cultivos y la deforestación causada por la expansión de la actividad humana en las últimas décadas. El conocimiento sobre paleoecología y la dinámica del paisaje es clave para entender los procesos del pasado que tuvieron un papel importante en el desarrollo de los ecosistemas y los paisajes ecuatorianos actuales. Sin embargo sólo un número limitado de estudios paleoecológicos de los Andes ecuatorianos están disponibles. En esta tesis se presentan análisis palinológicos que se llevaron a cabo en tres sitios diferentes en la región centro y sur de los Andes de Ecuador, con el fin de comprender mejor los últimos cambios en la vegetación, el clima y la dinámica del fuego; así como el impacto humano desde finales del Pleistoceno. El análisis del núcleo de sedimento El Cristal, ubicado en la ladera oriental de la cordillera Oriental en el Bosque Protector Corazón de Oro en el sureste del Ecuador, revela cambios en la distribución de la vegetación, el clima, el régimen de incendios y el impacto humano desde finales del Pleistoceno. Durante el Pleistoceno tardío el bosque montano fue el principal tipo de vegetación. Especialmente, hay evidencia de bosque de Polylepis lo que no ocurre en la actualidad. Sin embargo pruebas de proporciones relativamente altas de páramo sugiere que un bosque montano abierto ocupó la región. Por otro lado la presencia de taxones de páramo durante el Pleistoceno tardío, propone que la línea superior del bosque se encontraba a una altura inferior. Así mismo, la transición del Pleistoceno tardío al Holoceno temprano y medio se caracteriza por la presencia de bosque montano y una proporción estable de la vegetación de páramo. Sin embargo, después de aproximadamente 4000 cal yr BP, el bosque de Polylepis disminuyó, probablemente debido a un aumento en la frecuencia de incendios. Durante el Holoceno medio y tardío la composición de la vegetación cambió, el bosque montano fue menos frecuente y la vegetación de páramo se expandió. Altas proporciones de Asteraceae y Muehlenbeckia/Rumex (desde ca. 1380 cal yr BP) reflejan alteraciones del paisaje, probablemente por el impacto humano. Además, se registraron incendios durante todo el Pleistoceno tardío, pero fueron más frecuentes durante el Holoceno tardío, esto sugiere que eran de origen antropogénico. Por otro lado, El registro de polen Cajanuma valle, en la ladera occidental de la cordillera Oriental del Parque Nacional Podocarpus, sur de Ecuador, revela los cambios ambientales desde el último Glacial. Durante el último Glacial, páramo herbáceo principalmente dominado por Poaceae, Cyperaceae y Gentianaceae cubrió la zona. La línea superior del bosque se localizó a una altura más baja que la actual. El Holoceno temprano y medio se caracterizó por una sustitución parcial de páramo por bosque montano (Symplocos), el cual cambió su posición a elevaciones más altas donde está actualmente. Durante el Holoceno medio y tardío hay evidencia de un cambio de la vegetación, el páramo se re-expande con el predominio de Poaceae y alta presencia de Huperzia y Cyatheaceae. Durante el Holoceno tardío el páramo fue el principal tipo de vegetación que cubrió la zona. Los incendios se hicieron frecuentes desde el Holoceno tardío. Finalmente, el récord de polen Anteojos valle, que se encuentra en la ladera occidental del Parque Nacional Llanganates, en los Andes ecuatorianos centrales, presenta una reconstrucción ambiental detallada de aproximadamente los últimos 4100 años. La vegetación de páramo tuvo una ocurrencia dominante y estable en el área de estudio (Poaceae, Cyperaceae y Asteraceae); especialmente entre ca. 4100 - 3100 cal yr BP. Entre ca. 3100 - 2100 cal yr BP hubo una disminución de la vegetación de páramo seguido de una ligera expansión del bosque montano (Moraceae/Urticaceae, Trema, Celtis y Macrocarpaea). Desde ca. 2100 cal yr BP hasta la actualidad, la vegetación de páramo una vez más se hizo frecuente con una incidencia estable de los taxones del bosque montano. Se evidenció una baja frecuencia de incendios a lo largo del núcleo de sedimento; sin embargo, es evidente un ligero aumento entre ca. 4100 - 3100 años cal BP.

Riversleigh, World Heritage Property, located in North-western Queensland, Australia, contains over 200 fossil bearing localities from the Oligo-Miocene. The study presented here aims at finding new methods to improve the accuracy of palaeoecological and biochronological studies and describe the palaeoenvironmental and chronological settings of the Riversleigh fossil deposits. One of the methods developed in this thesis, Minimum Sample Richness (MSR), determines the minimum number of species that must be present in a fauna to allow meaningful comparisons using multivariate analyses. Using MSR, several Riversleigh localities were selected for a palaeoecological study using the cenogram method to determine the palaeoenvironment during the Oligo-Miocene. Finally, the Numerical ages method was used to refine the relative ages of the Riversleigh localities and a re-diagnosis of the Riversleigh Systems is proposed.

Trajectories of decline have been described in coral reefs throughout the Indo-Pacific region, with long-term losses of abundance, diversity and habitat structure. Since European settlement of the Queensland coastline in the mid-18th century, widespread changes in land use have occurred within Great Barrier Reef (GBR) catchments (e.g. extensive land clearing, agriculture and grazing). Despite direct and indirect evidence indicating decline of inshore reefs, it has proven difficult to ascertain links between land use changes, terrestrial discharge, water quality and the decline of coral reefs at regional scales, and the contributions of anthropogenic influences to the disturbance regimes of inshore reefs remains highly controversial. This thesis uses palaeoecological reconstruction of coral assemblages and high-precision U-Series dating to examine changes in community structure of inshore coral reefs in the Palm Islands region across decadal and centennial scales. Comparisons of modern and historical coral assemblages provide evidence of a collapse of Acropora coral communities at Pelorus Reef in the early 20th Century. Fossil assemblages in an adjacent site at Pelorus provide further evidence of an extrinsic shift from historical Acropora assemblages to more sediment-tolerant corals in modern assemblages, a change without precedence in 800 years of record. Sediment cores (2-5m length) were extracted from Pandora and Havannah reefs to determine long-term rates of reef growth throughout the late Holocene. Computer Axial Tomography (CAT) scans of cores revealed a framework dominated by coral fragments, and U-Series dating of corals revealed rapid and continuous reef growth at both reefs throughout the last 1000 yrs. Comparisons of reef accretion (m ka-1) from cores with published accretion rates from early-mid Holocene inshore GBR reefs show that reef slope environments are now accreting at rates equal to and exceeding those of the last 8000 years. This result contradicts assumptions that inshore reefs are undergoing or have undergone natural trajectories of geomorphic decline. A bayesian approach to determine stability of coral communities from the Pandora and Havannah cores indicates that those coral communities have existed in stable states for upwards of 400yrs, punctuated by periods of instability. Contrary to some paradigms of biodiversity, the high diversity communities were unstable on centennial scales, 4 yet the low diversity assemblages did not necessarily confer stability to these assemblages. Growth rates of inshore reefs were independent of diversity or community structure. From a management perspective, these results provide a longer-term (decades to centuries) understanding of coral community dynamics on inshore reefs of the GBR that provides a basis for detecting and understanding changes following European settlement, and a baseline for the management and potential restoration of coral communities at local and regional scales.

This thesis refines and develops understanding of the ecological and climatic characteristics of early Middle Pleistocene (MIS 19-13, c. 780-430 ka) interglacial environments in Britain. This period is characterised by globally muted (i.e. low amplitude) glacial-interglacial cycles, which increased in amplitude c. 430 ka with the Mid-Brunhes Transition (MBT). However, the influence of these global climatic characteristics on climates and ecology at regional and local scales is yet to be fully understood. Local ecological processes, particularly disturbance processes, have also received limited attention in pre-Holocene interglacial settings, despite their likely importance for vegetation and habitat structure. Chapters 4, 5 and 6 present in-depth multi-proxy palaeoenvironmental studies from three early Middle Pleistocene sites: West Runton, Pakefield and Brooksby. A combination of Coleoptera, pollen, coprophilous fungal spores, microcharcoal and sedimentology is used to reconstruct local ecological attributes for each site. Multivariate analyses of these datasets indicate the importance of disturbance processes (herbivore activity, wildfire, hydrogeomorphic processes) in driving and maintaining local vegetation structure and habitat heterogeneity. This is explored further (in Chapter 8), emphasising the apparent importance of site-specific factors, rather than those shared between sites, in determining the relative influence of each disturbance factor. In Chapter 7, new approaches to the coleopteran Mutual Climatic Range (MCR) method are applied to a suite of coleopteran records from interglacial sites spanning the Middle and Late Pleistocene (c.712-126 ka, MIS 17-5e). Summer temperatures, winter temperatures and temperature seasonality are reconstructed, to test whether there is evidence for MBT expression in Northwest European thermoclimates. No evidence for this is found, and it is suggested (in Chapter 8) that MBT expression in this region may instead be reflected in hydroclimatic variables (e.g. enhanced annual precipitation). Finally, it is suggested that disturbance processes and potentially wetter climates were beneficial to contemporary Lower Palaeolithic populations in Northwest Europe.

Aim: Mammals on islands often undergo remarkable evolutionary changes. The acquisition of ‘low gear’ locomotion, namely short and robust limb elements, has been typically associated with the island syndrome in large mammals and, especially, ruminants. Here we provide an investigative framework to examine biotic and abiotic selective factors hypothesized to influence evolution of this peculiar type of gait. Location: Islands worldwide. Taxon: Bovidae. Methods: We calculated response variables associated with ‘low gear’ locomotion in 21 extinct and extant insular bovids. We assembled data on the physiography of 11 islands and on life history and ecological traits of the focal taxa. We estimated 10 predictors (island area and four topographic indices, body mass, body size divergence, number of predators and competitors, large mammal richness) and used multiple regressions, regression trees, and random forests to assess their contextual importance. Results: The acquisition of ‘low gear’ locomotion generally happens on islands with a small number of competitors. However, the roughness of the island terrain appears to be also important, without being a main driver. Finally, although the most extreme cases of ‘low gear’ locomotion occurred on islands with no mammalian predators, our models show a non-significant relationship with this factor. Main conclusions: The evolution of ‘low gear’ locomotion in insular ruminants does not simply result from phyletic dwarfing and predatory release. Variation in morphological responses within Bovidae to ecological and topographic traits suggests, instead, a complex interplay of biotic and abiotic factors. Current understanding on the main drivers of species evolutionary pathways and biogeographic patterns are disproportionally based on few taxa, mainly vertebrates, and in some extreme cases (like this one) even on few species. Here we show how adding more data, even within the same taxonomic group, can challenge historically accepted macroevolutionary and macroecological concepts.

No / In an earlier study, stress lines in primate teeth were found to occur on a recurrent basis, probably corresponding to seasonal fluctuations in environmental parameters, such as food availability (Macho et al., J. Hum. Evol. 30 (1996) 57¿70). In the present study this approach was extended to the study of teeth of extant and extinct mammals, with the specific aim to determine the pattern of seasonality at the Australopithecus anamensis-bearing site at Allia Bay, Kenya. It was found that extant and extinct species, who share similar dietary/ecological adaptations, are comparable in their patterns of stress. Typical browsers/mixed feeders were found to exhibit three recurrent disturbances per year, whereas grazers usually only exhibit two. The average spacing between lines is also comparable between extant and extinct species. Hence, while the severity and predictability of the seasons probably fluctuated during crucial periods of hominin evolution, there is little doubt that all hominins lived in a seasonal environment. At Allia Bay, the pattern of stress lines found in mammals suggests that the environmental conditions in which A. anamensis lived may have been comparable to those found in the Masai Mara today.

Huber identified in samples from the forests of central Europe features for characterising by their wood structure the two species of British oak. We have confirmed for recently felled oaks the suitability of his method of analysis and applied it to timbers from ancient buildings and to samples from sub-fossil oaks. The two species appear to have persisted in separate locations during the last ice age. Such analysis of the numerous Holocene oaks in Europe now being dated by den - drochronology offers the possibility of studying the separate migration of the species.

No description available.